How to use edx-search?

Hello all,
Can anybody tell me the difference between field_dictionary and filter_dictionary of edx-search?

Another question:
I have 2 users named: Test User1 & Test User2
If I search Test then I am getting both of the users in search result that is fine
but If I search Test User1, still getting both users in the search result.
I want Test User1 in the search result.

Any idea about this?